Chapter 9: Gravity (from Lecture Slide) Flashcards
Newton discovered that gravity is
Universal
Newton hypothesized that the moon is
Constantly falling towards Earth
Compared motion of the moon to that of a cannonball being
Fired from the top of a high mountain
If fired fast enough, the cannonball would
Fall around the Earth (satellite)
Aristotle’s time:
Motion of planets and stars is natural
Aristotle’s time not governed by
The same laws as objects on Earth
Newton is recognized that
A force directed toward the Sun because it must act on planets and other celestial bodies
Newtonian synthesis
The same set of laws apply to both celestial and terrestrial objects
Law of Universal Gravitation
Everything pulls on everything else
Every body attracts every other body with a force that is
Directly proportional to the product of their masses and inversely proportional to the square of the distance separating them
The Universal Law of Gravity: Proportionality relationship
1) Constant r
2) Constant m1 and m2
1) Constant r
The greater the masses m1 and m2 of two bodies, the greater the force of attraction between them
2) Constant m1 and m2
The greater the distance of separation r, the weaker the force of attraction
Gravitational force is
The weakest of the 4 fundamental forces
Four fundamental forces are included:
1) Gravitational force
2) Weak force
3) Electromagnetic force
4) Strong force
The gravitational constant G, which links force with mass and distance, is universal because
It is the same everywhere in the universe, and this universality feature pi (r)
The gravitational force between you and the Earth is much
Greater
The weight at the Earth’s surface is
The same as the gravitational force between you and the Earth at Earth’s surface
Acceleration due to gravity, g
1) Directly proportional to the mass of the Earth
2) Inversely proportional to the square of the distance from the center of the Earth
Inverse square law: gravity and distance
1) Intensity of an effect is inversely proportional to the distance from the source
2) Newton law of gravitation, electrostatic, light, sound and radiation phenomena follow an inverse square law
For increase in distance, there are decreases in
Force (intensity)
At great distance, force approaches but never reaches
Zero
The force of gravity between two planets depends on their
Masses and separation distance
Weight
Force an object exert, against a supporting surface
Standing on a scale in an elevator accelerating downward, less compression in scale springs, Weight is:
Less
Standing on a scale in an elevator accelerating upward, more compression in scale springs, Weight is:
Greater
At constant speed in an elevator, no change in
Weight
When you stand still on a bathroom scale that is supported on a stationary floor, this tells that
Your weight is at rest
Gravitational force between you and Earth pulls you
Against the supporting floor and the scale